The long term objective of this project is the design of liposomes which can be employed clinically as carriers for anti-tumor agents. Within this framework we are conducting a systematic study of the factors that influence the uptake of liposomes by a normal and transformed cell pair, namely, 3T3 and SV1013T3. The thesis of this proposal is that such studies can provide the information on how to modify the liposomal membrane to achieve preferential uptake by the transformed cell line. The in vitro studies extended to include also a mouse leukemia line, L1210, will be compared with in vivo studies using L1210 tumor-bearing mice. For in vivo experiments, liposomes carrying (H3) actinomycin D will be employed to study the blood clearance and tissue distribution.